Hi folks,
Following on from the founding of the cross-distro ARM mailing list,
I'd like to propose an ARM summit at this year's Linux Plumbers
conference [1]. I'm hoping for a slot on Thursday evening, but this
remains to be confirmed at this point.
We had some lively discussion about the state of ARM Linux distros at
the Linaro Connect [2] event in Cambridge last week. It rapidly became
clear that some of the topics we discussed deserve a wider audience,
so we're suggesting a meetup at Plumbers for that bigger
discussion. The initial proposed agenda is:
* ARM hard-float
+ What is it and why does it matter?
+ How can distributions keep compatible (i.e. gcc triplet to
describe the port)?
* Adding support for ARM as an architecture to the Linux Standard
Base (LSB)
+ Does it matter?
+ What's needed?
* FHS - multi-arch coming soon, how do we proceed?
* 3D support on ARM platforms
+ Open GL vs. GLES - which is appropriate?
but I'm sure that other people will think of more issues they'd like
to discuss. :-)
If you wish to attend, please reply to the cross-distro list and let
us know to expect you. Make sure you're registered to attend Plumbers
Conf, and get your travel and accommodation organised ASAP.
[1] http://www.linuxplumbersconf.org/2011/
[2] http://connect.linaro.org/
Cheers,
--
Steve McIntyre steve.mcintyre(a)linaro.org
<http://www.linaro.org/> Linaro.org | Open source software for ARM SoCs
Hi,
Sorry for the cross post and long email :-)
Currently I am working on a very initial state build of Mandriva for arm.
Thanks to Jeff Johnson for giving me ssh access to armv7 hosts, and
Matthew Dawkins for building several Mandriva/Unity linux armv5
packages.
What I am trying to understand now is about choice of float abi.
I understand that the IHI0042D_aapcs.pdf file I donwload says
to use vfp registers for float/double arguments, but softfp seems
too good to miss, as armv5 should be around for some time yet.
So, I have two chroots, running:
softfp# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/armv7l-mandriva-linux-gnueabi/4.6.1/lto-wrapper
Target: armv7l-mandriva-linux-gnueabi
Configured with:
/home/pcpa/bootstrap/rpmbuild/BUILD/gcc-4.6-20110722/configure
--prefix=/usr --build=i586-mandriva-linux-gnu
--host=armv7l-mandriva-linux-gnueabi
--target=armv7l-mandriva-linux-gnueabi --enable-werror=no --enable-cxx
--with-cpu=cortex-a8 --with-tune=cortex-a8 --with-arch=armv7-a
--with-float=softfp --with-fpu=vfpv3-d16 --with-abi=aapcs-linux
--enable-languages=c,c++ --enable-threads=posix --disable-libssp
--disable-libmudflap
Thread model: posix
gcc version 4.6.1 20110722 (Mandriva) (GCC)
thumb# gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/armv7l-mandriva-linux-gnueabi/4.6.1/lto-wrapper
Target: armv7l-mandriva-linux-gnueabi
Configured with:
/home/pcpa/bootstrap/rpmbuild/BUILD/gcc-4.6-20110722/configure
--prefix=/usr --build=i586-mandriva-linux-gnu
--host=armv7l-mandriva-linux-gnueabi
--target=armv7l-mandriva-linux-gnueabi --enable-werror=no --enable-cxx
--with-cpu=cortex-a8 --with-tune=cortex-a8 --with-arch=armv7-a
--with-mode=thumb --with-float=hard --with-fpu=vfpv3-d16
--with-abi=aapcs-linux --enable-languages=c,c++ --enable-threads=posix
--disable-libssp --disable-libmudflap
Thread model: posix
gcc version 4.6.1 20110722 (Mandriva) (GCC)
This is unmodified upstream gcc, and using a set of bootstrap
scripts from a git branch I made on a checkout of
git clone git://fedorapeople.org/~djdelorie/bootstrap.git
Since I am still very "arm noob" :-) and just yesterday did
the thumb build to learn about thumb, so far, my impression
is that the best approach should be to use thumb+softfp.
Just so you know I am running thumb and arm builds, with
thumb using hard float and the softfp with arm instructions set:
softfp# objdump -d /usr/lib/libm.so | less
[...]
00008d30 <__ieee754_atan2>:
8d30: e3a0c000 mov ip, #0
8d34: e347cff0 movt ip, #32752 ; 0x7ff0
8d38: e92d4030 push {r4, r5, lr}
8d3c: ed2d8b10 vpush {d8-d15}
8d40: e3a05000 mov r5, #0
8d44: ec432b18 vmov d8, r2, r3
8d48: e3475ff0 movt r5, #32752 ; 0x7ff0
8d4c: e003c00c and ip, r3, ip
8d50: e15c0005 cmp ip, r5
8d54: e24dd02c sub sp, sp, #44 ; 0x2c
8d58: e1a04003 mov r4, r3
8d5c: ec410b19 vmov d9, r0, r1
8d60: e1a05002 mov r5, r2
8d64: 0a000022 beq 8df4 <__ieee754_atan2+0xc4>
[...]
thumb# objdump -d /usr/lib/libm.so | less
[...]
00007884 <__ieee754_atan2>:
7884: 2100 movs r1, #0
7886: 2000 movs r0, #0
7888: f6c7 71f0 movt r1, #32752 ; 0x7ff0
788c: ec53 2b11 vmov r2, r3, d1
7890: f6c7 70f0 movt r0, #32752 ; 0x7ff0
7894: 4019 ands r1, r3
7896: 4281 cmp r1, r0
7898: e92d 03f0 stmdb sp!, {r4, r5, r6, r7, r8, r9}
789c: ed2d 8b10 vpush {d8-d15}
78a0: 461c mov r4, r3
78a2: b08a sub sp, #40 ; 0x28
78a4: eeb0 8b41 vmov.f64 d8, d1
78a8: 4616 mov r6, r2
78aa: eeb0 9b40 vmov.f64 d9, d0
78ae: d03c beq.n 792a <__ieee754_atan2+0xa6>
[...]
I am kind of trying to figure what "The Industry" says about it,
and just checked the linaro gcc-4.6 relevant changes for me
right now, that are...
+ --with-arch=armv7-a --with-tune=cortex-a8 \
+ --with-float=$(float_abi) --with-fpu=neon \
+# check if we're building for armel or armhf
+ifeq ($(DEB_TARGET_ARCH),armhf)
+ float_abi := hard
+else ifneq (,$(filter $(DEB_TARGET_ARCH), arm armel))
+ float_abi := softfp
+endif
If I understand correctly, neon will have better support for
simd instructions right?
Either way, I used two simple benchmarks to try to sell
myself the idea of breaking compatibility with armv5 or
older binaries, but still not convinced, but, as I said, we
should use whatever "The Industry" chooses :-)
I used for benchmark http://www.tux.org/~mayer/linux/bmark.html
and http://www.linuxfordevices.com/c/a/Linux-For-Devices-Articles/Why-ARMs-EABI…
and also compared with my home computer (quad)core i5 x86_64,
and attached results...
Thanks and again sorry for cross posting and long email,
Paulo
David:
On Wed, Aug 24, 2011 at 6:55 PM, <david(a)lang.hm> wrote:
> ARM is currently in worse shape than the PC market ever was in this aspect,
> but in this case it's less a matter of getting the hardware guys to change
> what they do than it is to get better documentation of what the hardware is
> really doing and not duplicating drivers for cases where the right answer is
> just replacing a constant with a variable (just as an example of the very
> common case where the same component is wired to a different address)
I agree.
Maybe Linaro or an equivalent organization could provide a "ARM kernel
janitor" service to the community, where they refactor existing ARM
platform/driver code to make it more common. This is something that's
difficult for a single person with experience in only one or two SoCs
to do, but it would be pretty straightforward work for a team of three
or four people with broad coverage of the SoC devices the kernel
supports now.
As such refactoring consolidated larger and larger chunks of kernel
code, new designs would gravitate towards those consolidated
implementations because they would be the dominant references.
b.g.
--
Bill Gatliff
bgat(a)billgatliff.com
On Tue, Aug 23, 2011 at 02:41:32PM -0500, David Mandala wrote:
>On 08/23/2011 11:11 AM, Steve McIntyre wrote:
>> UPDATE: we've not had many people confirm interest in this event yet,
>> which is a shame. If you would like to join us for this session,
>> please reply and let me know. If we don't get enough interest by the
>> end of Sunday (28th August), then we'll have to cancel the meeting.
>>
>> Cheers,
>I will be attending
Thanks David.
Cheers,
--
Steve McIntyre steve.mcintyre(a)linaro.org
<http://www.linaro.org/> Linaro.org | Open source software for ARM SoCs
On Mon, Aug 01, 2011 at 02:34:56PM -0400, DJ Delorie wrote:
>
>> I haven't looked at the docs in a while, but we are most likely going
>> to need this again in the distant future. Plus the fact it seems to
>> come up all the time.
>
>One of the things I'm hoping we get out of this is an official fully
>automated way to bootstrap, make it fast, and do it often. Then it
>will always be there when we need it.
Sounds like an excellent idea. :-)
We're working on a similar goal within Debian too.
Cheers,
--
Steve McIntyre
steve.mcintyre(a)linaro.org
